Widespread and potentially catastrophic areal flooding and river flooding is expected this afternoon through Wednesday morning in Eastern Oklahoma, Western Arkansas, Western Louisiana, and Southwest Missouri, warns the National Weather Service in Tulsa, Oklahoma, in their latest flood watch for the region. The storm system responsible is a massive, slow-moving trough of low pressure over the Western U.S. that dumped heavy snows that closed several interstate highways in Arizona over the weekend. This storm system will collide with the warmest and moistest air mass ever recorded in March in the Central and Eastern U.S. According to the NWS in Minneapolis, Minnesota, moisture flowing northwards into Minnesota along the cold front yesterday had the highest levels of moisture ever recorded so early in the year, and moisture levels are expected to remain at record levels today. At the boundary between the Western U.S. trough of low pressure and Central U.S. ridge of high pressure, a cold front will lift huge quantities of moisture-laden air aloft, forcing record rains to fall. A wide region of 4 - 8 inches of rain is expected in the flood watch area, and isolated amounts as high as 15 inches could fall by Wednesday, as numerous rounds of thunderstorms repeatedly track over the same area. The cold front is also expected to trigger a Moderate Risk of severe weather over much of Texas today, including the Dallas-Fort Worth area, says NOAA's Storm Prediction Center. Damaging winds, large hail, flash flooding, and few strong tornadoes are expected to affect the area late this afternoon. Severe thunderstorm watches are already posted for much of West Texas, as seen on our Severe Weather Map. Eleven tornadoes were reported yesterday in Oklahoma, Nebraska, and South Dakota.

Figure 1. Predicted rainfall amounts for the 3-day period Monday morning through Thursday morning show an area of 7+ inches (yellow colors) is expected over Eastern Oklahoma, Western Arkansas, Western Louisiana, and Southwest Missouri. Image credit: NOAA HPC.

Figure 2. NOAA's Storm Prediction Center has highlighted a Moderate Risk area for severe weather over much of Texas today, including the Dallas-Fort Worth area.

Summer in March for the MidwestThe ongoing March heat wave in the Midwest is one of the most extreme heat events in U.S. history. With so many records being shattered, it is difficult to cover in detail just how widespread, long-lasting, and extreme the event is, and I offer just a few highlights:

Winner, South Dakota hit 94°F yesterday, the earliest 90°+ reading ever recorded in the Northern Plains, according to wunderground's weather historian, Christopher C. Burt. The 94°F reading was just 2°F short of the all-time state record for South Dakota in March, which was 96°F in Tyndall in 1943. However, subsequent analysis by NOAA questioned this 94°F reading, and it is now believed that 87°F is the appropriate high for Winner.

International Falls, Minnesota hit 79°F yesterday, the hottest March temperature on record in the Nation's Icebox. At midnight this morning, the temperature was 66°F there, breaking the record high for March 19 (set in 1910) by 6°F. The low temperature for International Falls bottomed out near 60°F this morning, so low for today is (unofficially) the same as the previous record high for the date. This is the seventh consecutive day that International Falls has broken or tied a daily record. That is spectacularly hard to do for a station with a century-long weather record. The longest string of consecutive records being broken I'm aware of is nine days in a row, set June 2 - 10, 1911 in Tulsa, Oklahoma (with weather records going back to 1905.) International Falls has a good chance of surpassing nine consecutive records this week.

Houghton, Michigan, near the frigid shores of Lake Superior, hit 76°F both Saturday and Sunday. It was the hottest March temperature on record, and an astonishing 44°F above the average high for the date (Saturday) of 32°. Huron, South Dakota also recorded a high temperature (88°F) that was 44° above the average high for the date, on Sunday. Most of the cities in Northern Michigan set all-time March high temperature records over the weekend.

Chicago, Illinois now has a string of five consecutive days of 80°+ temperatures, and the hottest temperature on record for so early in the year (82°F on Friday, and tied again on Saturday). The average high temperature in August is 82°F in Chicago, so this week is basically summer weather. Prior to this year, there had only been 10 days in March with highs in the 80s in Chicago, going back to 1871. The last time Chicago saw an 80 degree temperature during the month of March (prior to this year) was over 22 years ago back on March 12, 1990 when the high temperature hit 81. This morning's Public Information Statement from the National Weather Service in Chicago had this to say about this unprecedented March heat:

Chicago and Rockford have now both broken high temperature records 5 days in a row. There is even the potential they could tie or break record highs for up to an unbelievable 8 days in a row depending on how warm temperatures get Monday through Wednesday. It is extraordinarily rare for climate locations with 100+ year long periods of records to break records day after day after day.

Figure 3. March's month-to-date average temperature compared to the other top 5 warmest months of March in Chicago. The dotted blue lines are month-to-date average temperatures based on the current predicted temperatures. The hashed black line is the average month to date temperature for March. These graphs really illustrate just how far above the previous warmest top 5 Marches this month really has been and assuming no major pattern change the last week of the month gives some indication of just how far above the record March 2012 could end up being. Image credit: NWS Chicago.

Record heat in CanadaRecord-breaking heat has also penetrated into the Prairie provinces of Canada over the past week. Winnipeg, Manitoba broke its record high for the past four days in a row, and hit 21°C yesterday, its hottest temperature on record so early in the year. With today's forecast by Environment Canada and wunderground both calling for highs near 25°C (77°F), Winnipeg is likely to record its highest March temperature on record. Previous record: 23.3°C on March 27, 1946. The earliest date for a 25°C+ temperature in Winnipeg is April 9, 1977.

Figure 4. The jet stream pattern features a large, southwards dipping bulge over the Western U.S., creating a trough of low pressure with cold and snow, and a large, northwards looping bulge over the Central U.S., creating a record-strength ridge of high pressure.

Why the record early-season warmth?The unusual warmth is due to a loop in the jet stream that has created a large upper-level ridge of high pressure that is stuck in place over the Eastern U.S.--a phenomenon known as a "blocking pattern." Since the jet stream acts as the boundary between cold air to the north and warm air to the south, and the large loop in the jet places its axis far to the north of the eastern U.S., summer-like warmth has developed over the eastern half of the U.S. Conversely, colder than average temperatures have developed over the western third of the U.S. behind the southwards-dipping loop of the jet stream. There are at least three large-scale patterns working together right now to create an unusually strong ridge over the eastern half of the U.S.:

1) La Niña. The on-going La Niña event in the Eastern Pacific has weakened considerably over the past month, but ocean temperatures there are still cool enough to affect the jet stream pattern, favoring high pressure and warm temperatures over the Eastern U.S., and low pressure and cold temperatures over the Western U.S.

2) The Madden-Julian Oscillation( MJO). The MJO is a 2-month cycle of thunderstorm activity that travels west to east along the Equator. The MJO is currently in phase with La Niña, and is helping create warmer temperatures over the Eastern U.S.

3) The North Atlantic Oscillation (NAO.) The NAO is in its positive phase, which means the difference in pressure between the Icelandic Low and the Azores High is stronger than usual. This tends to increase the jet stream winds and keeps the jet from sagging southwards over the Eastern U.S.

While the blocking pattern responsible for the heat wave is natural, it is very unlikely that the intensity of the heat would have been so great unless we were in a warming climate. Climate scientist Dr. James Hansen has posted an interesting (as yet unpublished) paper discussing how the odds of such extreme heat events have shifted in recent years.

Extreme jet stream patterns like this often lead to tornado outbreaks in the Midwest, at the boundary of where warm, moist air flowing north from the Gulf of Mexico collides with cold, dry air flowing south. Cold dry air aloft, combined with warm, moist air at the surface, makes the atmosphere unstable, since air rising in thunderstorm updrafts will be less dense than the surroundings, allowing the air to accelerate upwards and increase the intensity of the thunderstorm. This will be the case today, when NOAA's Storm Prediction Center has highlighted a Moderate Risk area for severe weather over much of Texas today, including the Dallas-Fort Worth area.

Flood risk low this year for the Northern PlainsFor the first time in four years, the Northern Plains are not expecting major to record snow melt flooding, said NOAA's National Weather Service in their annual spring flood outlook issued last week. Residents along the Mississippi, Missouri, Red, and Souris Rivers have endured a punishing series of bad flood years, but this year is unlikely to continue that trend, due to a lack of snow cover. The Northern Plains states of Minnesota, Wisconsin, North Dakota, and South Dakota recorded their 3rd - 8th warmest winter in the 117-year record, and are on pace to crush the record for warmest March in history. Winter snowfall was below average over most of the region, and what snow was on the ground at the beginning of March has mostly melted, thanks to the record-breaking March heat this week. The Souris and Red River basins contain about one-third the amount of water in the snow as last year, ranking this season in the lower half of the last 60 years. Precipitation this water year (since Oct 1, 2011) has been less than 50% of the normal across the Upper Mississippi and Upper Missouri Valleys, and much of the region is under moderate to severe drought, according to the latest Drought Monitor.

Figure 5. What a difference a year makes! Snow cover on March 15 of last year (top) was heavy over Minnesota, Wisconsin, and the Dakotas, and caused massive flooding problems on the Mississippi and Missouri Rivers during spring melt season. In contrast, there is almost no snow pack in the Upper Midwest this year (bottom), significantly reducing the odds of spring flooding on the Missouri and Mississippi Rivers. Image credit: NOAA/NOHRSC.

I pulled a piece of ice out of Mullet Lake in Northern Michigan during my bike ride along the shore. It was so strange riding shirtless in 82°F heat along the shore of a frozen lake. The ground still had some snow patches from the 16" snow storm from last week. The lake ice is breaking up weeks ahead of usual due to our warm winter and incredible March heat.

Quoting hurricanehunter27: That's what I'm thinking. For some reason I keep on reading it as you want strong tornadoes in high populated areas. I know that is not what you mean but I keep reading it that way. I think I just need some sleep.

That's what I'm thinking. For some reason I keep on reading it as you want strong tornadoes in high populated areas. I know that is not what you mean but I keep reading it that way. I think I just need some sleep.

Quoting TropicalAnalystwx13:Many conditions are coming together for a sizable tornado outbreak this evening and into the overnight hours across much of central Texas into southeastern Oklahoma. This really appeals to me because we're going to have potentially strong tornadoes tracking across relatively populated areas. I have a feeling Austin and DFW (where I used to live) will be targeted...but I hope not.

Barbara Bush has been frequently stereotyped as something of an Ice princess...although I must say: I have a very close friend who was on her Secret Service detail...and he says she was totally lovely...even baked cookies for the agents...

Quoting MississippiWx:La Nina is trying to hold on as cold anomalies have fought back off the South American coastline. As I and many others have said before, an El Nino will be slow to occur if one occurs at all.

George Bush is a heck of alot better person then you will ever be. A truely good person has no need to bash others. Keep that in mind next time you try to bring yourself lower with comments such as that.

Sheesh, I'm a card carrying Republican and I found what press said hilarious.

Former President George W. Bush announced today he will become an outspoken climate change advocate. He became alarmed when a large chunk of ice fell off his mother.

George Bush is a heck of alot better person then you will ever be. A truely good person has no need to bash others. Keep that in mind next time you try to bring yourself lower with comments such as that.

I feel as though a lot of the United States are going to be in store for a very hot summer. The jet stream is displaced so anomalously far north that there shouldn't be any significant cold intrusions until next fall. Looks like an upper level ridge will develop by mid-April and encompass much of the eastern two-thirds of the U.S. through September. Pattern bears a lot of similarities to the one present in Russia during spring/summer 2010 and in the Southern Plains last spring & summer. Temperatures could average 5 to 10 degrees above normal in many locations through September. If you thought last summer (which was the 3rd warmest on record) was bad, just wait for what's coming this year. It will be a shock to many Americans, but not unexpected for those of us familiar with the scientific literature (such as the recent Stanford study showing that, within 30 or 40 years, at least every other summer will be hotter than the hottest summer previously recorded in the U.S.).

The only fly in the ointment is if an El Nino were to rapidly develop, as that could have significant implications on the path of the jet stream preventing the upper-level ridge from becoming very firmly entrenched & self-perpetuating.

Many conditions are coming together for a sizable tornado outbreak this evening and into the overnight hours across much of central Texas into southeastern Oklahoma. This really appeals to me because we're going to have potentially strong tornadoes tracking across relatively populated areas. I have a feeling Austin and DFW (where I used to live) will be targeted...but I hope not.

Quoting OracleDeAtlantis:Along the upper southeastern coastline, our evergreen azaleas are blooming about a month ahead of schedule this year.

Considering our milder than average winters, due to the Gulf Stream about 70 miles off shore, I'm perplexed. I was always taught that much of the spring growth and flowering was tied to the length of the day, not temperature. We're also way behind on soil precip., adding to the mystery. We've been in the "Extreme category" all winter having recently been upgraded to "Severe," due to a couple of 1-2" rains.

Something else I've noticed, which is stranger than the azaleas, are the mosquitoes. We've had enough recent rains to allow some replacement of the local swamps, but not enough to allow the accumulation in say ... old tires, and other places that mosquitoes like to lay their eggs. They tend to avoid bodies of water large enough to have predators, if they can help it, preferring smaller bodies of water that are less risky, but which provide the food their larva will need.

We've recently had our window screens off, and some of these doors and windows open, and the house fills up every day with large female mosquitoes, but they're not biting. It's weird, they seem to be more attracted to the shelter of the interior of the house, but they're not interested in us in the least. Outside also, in areas where I would normally expect to be bitten ... nothing. I know they are there, they're just not biting. These are clearly the females who have hibernated. These aren't new hatchlings, so perhaps this makes the mystery easier to understand. The older females aren't attempting to lay their eggs.

It seems like I may have experienced this phenomena in the spring-time before, but not like this. I've caught several females in the house, and there's no blood in them ... in case my wife and I are just imagining not being bitten.

So why aren't they biting? I'm thinking they know something .... like .... NO WATER is forthcoming. I'm thinking ... extended drought, and they know it way before we know it.

How do you know the mosquitoes are female? Only females bite, so I would hazard a guess that these are male mosquitoes. Maybe hanging around looking for females. What better place than near the food?:)

Here's an update from KVUE Meteorologist Mark Murray: It's been several years since we've seen this great of a risk of severe weather in Central Texas. The Storm Prediction Center has placed the Austin area in a Moderate Risk, which is rather unusual for us. Starting around 6:00 pm tonight, we could see severe storms which may contain large hail of 1"-2" in diameter, damaging winds, and tornadoes. Strong tornadoes are possible in this type of situation. After midnight, we'll see an increased risk of flash flooding as the rain continues. Many areas could see 2"-4" with isolated totals of 5"-6", especially north and northeast of Austin. Things should settle down around 6:00 am Tuesday. It will be very important to keep track of the weather tonight. And I would appreciate your reports here on Facebook, especially reports and pictures of large hail, flooding, and of course tornadoes, but only if you can do so safely. The best place to send pictures would be to spotnews at KVUE dot com. It's going to be a long night!!

Pretty strong langugage from Dr. Murray...he is usually the conservative, reserved Austin area forecaster!

Quoting 1900hurricane:I'm probably going to drive up to Hearne in the next hour or so to wait and see if anything starts to fire up. Hearne is a good spot for me to start. It has many crossroads, so I can go in pretty much any direction that I need to, plus it's really close to College Station so I can just go home if nothing worth chasing develops.

Good ol Hearne, TX. I just moved to Dallas from Franklin so I know that area well. Good luck on catching a decent storm today. I'm hoping to see one myself, only from the view of my office window in downtown.

Either way Houston Metro is going to get dumped on. My guess is 2" to 3" but like you said the key will be where does the front slow down because where ever this happens is where very severe flooding could occur.

Yes indeed. I just went and bought a new weather radio also. I can't wait to get it set up lol. My old one was pretty darn old